Add new config-option 'migrate_passwords' in section 'web'... ...to auto-migrate passwords at web-login time. Default for the new option is "yes" so if you don't want that passwords are auto-migrated to a more secure password scheme on user login, set this to "no" before running your tracker(s) after the upgrade.

#!/usr/bin/env python
import zlib, base64, sys
print base64.encodestring(zlib.compress(sys.stdin.read()))